Examples of near eye display applications include head-mounted displays (HMDs) for wearable computers or the like, and Eyetap devices for recording activities as viewed by a user (so-called “souveillance” devices). Devices of this type, exemplified by devices such as associated with the Google™ Project Glass™ devices, may take the form of eyeglass frames worn by a user and including an optics element positioned for viewing directly by the eye. The devices may include a beam splitter to enable the eye to view displayed data superimposed either on an image directly viewed by the eye through a transparent display or on an image recorded by a camera having a same line of sight as the eye and reproduced on the display to provide a view similar to an otherwise directly viewed image. The effect may be like that of conventional heads-up displays (HUDs), such as historically used for aircraft landings, etc. In a simpler Eyetap implementation, display functionality may be omitted, and the beam splitter may simply serve to divert light to enable a camera to capture the same scene seen by the eye looking through the splitter.
The eyeglass frames supporting the HUD may be traditionally configured with a generally horizontal portion extending laterally across the face at the base of the eyebrows, supported centrally on the nose by nose pads and supported at each end on the ears by generally perpendicularly extending contoured temple pieces. The display optics may be located in an injection molded cavity formed integrally with the frame and have a viewing aperture located for viewing by at least one of the eyes as, for example, without requiring the user to look substantially away from the user's usual ambient environment viewing perspective. The frame may include eyeglass lenses or have no lenses.
In the case of a head-mounted display for a wearable computer or cellphone, the eyewear or other head-mounted display apparatus may also include some functionality for wired/wireless interconnection with a CPU and also for an interface capability. In some cases, the included functionality may include eye movement tracking capability to enable interactivity between the user and the display/computer elements. For example, in the case of display placement out of a direct forward line of sight of the user, eye movement tracking capability may be useful for implementing a circuit “wake-up” mode to activate selected features of the display only when a user is actually viewing the display and conserve power by entering a “sleep” mode when the user's eye is closed or directed elsewhere. Eye movement tracking may also be used as an intentional user input mechanism for implementing a sequence of commands in response to a corresponding sequence of eye movements. In cases where the eyewear includes elements for recording what the user sees, eye movement tracking may be used to direct the line of sight, focus point or lens aperture opening of the camera to follow the line of sight, focus point or pupil aperture opening of the viewer.
Power consumption and interactivity are two key factors in the design of apparatus for near eye display applications. Eye tracking addresses both these factors; however, conventionally implementations, such as those using liquid crystal on silicon (LCoS) display and liquid-crystal display (LCD) elements, have required the use of external cameras which has limited compactness and increased complexity of the systems.
Existing systems for near eye display systems are disclosed in U.S. Pat. No. 8,235,529; H. Hong & C. Gao, “A compact eyetracked optical see-through head-mounted display,” in Displays and Applications XXIII, Proc. SPIE 8288 (2012); T. Järvenpää & V. Aaltonen, “Compact near-to-eye display with integrated gaze tracker,” in Photonics in Multimedia II, Proc. SPIE 7001 (2008); and C. Curatu, H. Hua & J. Rolland, “Projection-based head mounted display with eye tracking capabilities,” in Novel Optical Systems Design and Optimization VIII, Proc. SPIE 5875, pp. 128-140 (2005) (see also U.S. Pat. No. 7,522,344); the entireties of all of which are hereby incorporated herein by reference.
Additional background information is disclosed in U.S. Pat. Nos. 6,456,262; 6,926,429; 7,091,867; 7,331,671; 8,125,558; U.S. Patent Application Publication Nos. 2005/0007552; 2007/0040921; 2010/0220291; 2011/0058084; 2011/0176797; 2011/0234859; 2012/0154595; 2013/0044042; 2013/009853; and PCT Patent Application Publication Nos. WO 2011/018655 and WO 2013/025672; the entireties of all of which are also hereby incorporated herein by reference.